I know how to get back a working file-system(FS), the usual way, by running
e2fsck -b alt_SB_no /dev/sdX
which will fix my FS.
I have an ext4 image-file that is corrupt - I want to patch in just the Super Block. I want to mount it via loop using an alternate super-block number. I DO NOT want to alter the image beyond a SuperBlock.
How do I do this?